The present invention relates to a sealing apparatus for containers where air is exhausted to a required depressurized (vacuum) status.
Generally, in heat-treating apparatuses, vacuum pumps are used to exhaust air to a required depressurized status. When this is done, a method commonly used in semiconductor manufacturing, for example, involves arranging O-rings comprising fluoride rubber or the like between the manifold and the process tubes for process containers, thereby maintaining air-tightness of the process container.
Not only this, Japanese Patent Application Laid Open No. 123336-1989, for example, proposes a sealing method wherein a furnace opening portion of a pressure-reduction CVD (chemical vapor deposition) apparatus has air-tightness maintained by an inner-side O-ring and an outer-side O-ring respectively provided to a contact portion of a seal cap for opening and closing the furnace opening and the furnace opening flange, and the contact portion of the furnace opening flange and the reaction tubes, then the space between the two O-rings is communicated with a vacuum opening.
Furthermore, Japanese Utility Model Application Laid Open No. 188135-1987, for example, proposes a sealing method which comprises two O-rings made of a material deteriorated by the furnace temperature and inserted through spacers into the gap between the glass reaction tubes and the door flange of the reaction furnace of a pressure-reduction CVD apparatus, thereby ensuring air-tightness. A rotary pump or the like is used to exhaust air from the space surrounded by the two O-rings and the glass tubes and the door flange via the spacers.
As has been described above, with the conventional sealing technologies, O-rings made from flexible fluoride rubber or some other material which deteriorates easily due to heat are used as the material of the sealing members of the seal portion of the process container. Thus, there are the following problems. More specifically, the heat resisting temperature of O-rings of this type is generally about 200.degree. C. and so when the sealing portion of the heat-treating apparatus is heated to temperatures above this, the O-rings melt and deform so that there is the problem that it is not possible to obtain the required vacuum effect.
In addition, when the operation of the heat-treating apparatus is stopped and the O-rings used in the sealing portion thereof are exchanged, the O-rings are cooled and the O-rings themselves stick on other members of the sealing portion so that the removal of these O-rings becomes extremely difficult. Furthermore, in some cases, when the glass tubes or the like which comprise the members of the process container are removed from the container, there is the danger that these glass tubes may be damaged.
Not only this, the gas and water components included in the O-rings may be discharged during its use. The amount of this discharge changes according to the ambient pressure and temperature, and the processing time, and so when heat-treatment of the object being processed is performed by a process container using such O-rings as the sealing member, it requires much time to create a vacuum in the container after the pressure inside the process container has reached a required pressure. Then, if heat-treatment is not performed after the gas and water components from the O-rings have been sufficiently discharged, there is the problem that large differences may generate between processing lots of the objects being processed. In addition to this problem, there is also the problem that with reduction heat-treatment which uses a processing gas such as hydrogen (H.sub.2) or the like to remove natural oxide films from the objects being processed, there is further discharge of the gas and water components from the O-ring even if there is already sufficient discharge from inside the process container by a vacuum pump, resulting in that the required reduction heat-treatment can still not be performed.
In the light of these problems associated with the conventional technology, the present invention has as an object the provision of a sealing apparatus for a process container that can perform sealing so that there is no mixing of unnecessary oxygen and components from the atmosphere and that can maintain a sufficient airtightness.